tf_aws_bastion_s3_keys

A Terraform module for creating resilient bastion host using auto-scaling group (min=max=desired=1) and populate its ~/.ssh/authorized_keys with public keys fetched from S3 bucket.

This module can append public keys, setup cron to update them and run additional commands at the end of setup. Note that if it is set up to update the keys, removing a key from the bucket will also remove it from the bastion host.

Only SSH access is allowed to the bastion host.

Input variables:

name - Name (default, bastion)
instance_type - Instance type (default, t2.micro)
ami_id - AMI ID of Ubuntu (see samples/ami.tf)
region - Region (default, eu-west-1)
iam_instance_profile - IAM instance profile which is allowed to access S3 bucket (see samples/iam.tf)
s3_bucket_name - S3 bucket name which contains public keys (see samples/s3_ssh_public_keys.tf)
s3_bucket_uri – S3 URI which contains the public keys. If specified, s3_bucket_name will be ignored
vpc_id - VPC where bastion host should be created
subnet_ids - List of subnet IDs where auto-scaling should create instances
keys_update_frequency - How often to update keys. A cron timespec or an empty string to turn off (default)
additional_user_data_script - Additional user-data script to run at the end
associate_public_ip_address - Whether to auto-assign public IP to the instance (by default - false)
eip - EIP to put into EC2 tag (can be used with scripts like https://github.com/skymill/aws-ec2-assign-elastic-ip, default - empty value)
key_name - Launch configuration key name to be applied to created instance(s).

Outputs:

ssh_user - SSH user to login to bastion
security_group_id - ID of the security group the bastion host is launched in.

Example:

Basic example - In your terraform code add something like this:

module "bastion" {
  source                      = "github.com/terraform-community-modules/tf_aws_bastion_s3_keys"
  instance_type               = "t2.micro"
  ami                         = "ami-123456"
  region                      = "eu-west-1"
  iam_instance_profile        = "s3-readonly"
  s3_bucket_name              = "public-keys-demo-bucket"
  vpc_id                      = "vpc-123456"
  subnet_ids                  = ["subnet-123456", "subnet-6789123", "subnet-321321"]
  keys_update_frequency       = "5,20,35,50 * * * *"
  additional_user_data_script = "date"
}

If you want to assign EIP to instance launched by auto-scaling group you can provide desired eip as module input and then execute additional_user_data_script which sets EIP. This way you can use Route53 with EIP, which will always point to existing bastion instance:

module "bastion" {
  // see above
  eip = "${aws_eip.bastion.public_ip}"
  additional_user_data_script = <<EOF
REGION=$(curl -s http://169.254.169.254/latest/dynamic/instance-identity/document | grep region | awk -F\" '{print $4}')
INSTANCE_ID=$(curl -s http://169.254.169.254/latest/meta-data/instance-id)
aws ec2 associate-address --region $REGION --instance-id $INSTANCE_ID --allocation-id ${aws_eip.bastion.id}
EOF
}

resource "aws_eip" "bastion" {
  vpc = true
}

resource "aws_route53_record" "bastion" {
  zone_id = "..."
  name    = "bastion.example.com"
  type    = "A"
  ttl     = "3600"
  records = ["${aws_eip.bastion.public_ip}"]
}

After you run terraform apply you should be able to login to your bastion host like:

$ ssh ${module.bastion.ssh_user}@${module.bastion.instance_ip}

or:

$ ssh ${module.bastion.ssh_user}@${aws_eip.bastion.public_ip}

or even like this:

$ ssh ubuntu@bastion.example.com

PS: In some cases you may consider adding flag -A to ssh command to enable forwarding of the authentication agent connection.

##Authors

Created and maintained by Anton Babenko. Heavily inspired by hashicorp/atlas-examples.

License

Apache 2 Licensed. See LICENSE for full details.

james-gonzalez/tf_aws_bastion_s3_keys

tf_aws_bastion_s3_keys

Input variables:

Outputs:

Example:

License